Since the introduction of biodiesel fuel in South Africa prior to World War II, work has proceeded to increase its viability as a fuel substitute. In more recent years, environmental and economic pressures, (eg. events such as Oil Embargoes, and laws such as the Clean Air Act of 1990), have provided impetus for continued development. Most effort to date has been focused on waste minimization, by-product separation technology, and/or by-product utilization. This is best demonstrated by noting that production of Biodiesel fuel by a methyl-esterification process as applied to soy oil, produces an effluent stream with twenty (20%) percent crude glycerol content. Other desirable goals include production of biodiesel with cleaner burning properties and improved cold-temperature flow characteristics.
It is noted that Biodiesel fuel has been reported by Clark et al., in an article titled "Methyl and Ethyl Soybean Esters As Renewable Fuels For Diesel Engines", JAOCS, Vol. 61, No. 10 October 1984, to produce NO.sub.x emissions higher than produced by Diesel fuel. Additional related discussion is found in an article titled "Diesel Fuel Derived From Vegetable Oils, III. Emission tests Using Methyl Esters Of Used Frying Oil", by Mittelbach et al., JAOCS, Vol. 65, No. Jul. 7, 1988.
It is also noted that the use of biodiesel fuel, (ie. methyl esters of triglycerides), is limited in practice as it demonstrates a "Cloud Point" of near zero (0.0) degrees centigrade, (ie. thirty-two (32) degrees Fahrenheit), while the Cloud point of Diesel #2 is near negative sixteen (-16) degrees centigrade. A similar disparity exists with respect to the "Pour Point", which for Biodiesel fuels is near negative two (-2) degrees centigrade, while that for Diesel fuel is near negative twenty-seven (-27) degrees centigrade. This is discussed in an article titled "Low-Temperature Properties Of Triglyceride-Based Diesel Fuels: Transesterified Methyl Esters and Petroleum Middle Distillate/Ester Blends", by Dunn et al, JAOCS, Vol. 72, No. 8, 1995. These adverse cold temperature flow properties of Biodiesel fuel as compared to Diesel fuel, with accompanying reduced viscosity and low temperature flow lead to problems such as truck fuel filter plugging below thirty-two (32) degrees fahrenheit. The use of Biodiesel fuels can not become widespread unless this problem is overcome. Suggested solutions include Methyl Ester "winterization", which is discussed in an article titled "Reducing The Crystallization Temperature Of Biodiesel By Winterizing Methyl Soyate", by Lee et al., JAOCS, Vol. 73, No. 5, 1996; and application of biotechnology to produce biodiesel with improved specifications, as discussed in an article titled "Vegetable Oils: From Table To Gas Tank", by Chowdhury et al., Chem. Eng. February 1993. Such avenues of investigation might prove successful but as yet are of questionable industrial value.
As mentioned, esterification of soy oil to form Biodiesel produces approximately twenty (20%) crude glycerol as a by-product, and while uses for crude glycerol have been pursued, mostly in Europe, costly purification steps must typically he performed to produce even a low grade product of questionable value. Uses for said low grade product include mixing with animal manure to form a fertilizer, and mixing with feed for animals. This is discussed in an article titled "A Low Waste Process For The Production Of Biodiesel", Ahn et al., Sep. Sci. & Tech., 30(7-9) 1995. Research has shown that potential exists for use of bacteriologically transformed crude glycerol to form products useful in plastics production, ("Vegetable Oils: From Table To Gas Tank", by Chowdhury et al., Chem. Eng. February 1993). The most promising and economically viable use for crude glycerol might be, however, conversion into mono and di-fatty acid esters of crude glycerol. This is discussed in an article titled "Technical Uses Of Fatty Acid Esters", by Meffert, JAOCS, Vol. 61, No. 2, February 1984. This alternative might prove to be most beneficial in the economics of Biodiesel fuel production. To understand why this is the case, it must be understood that crude glycerol produced as a by-product in production of Biodiesel fuel via transesterification of triglycerides is inherently insoluble in the Biodiesel Fuel.
Patents of which the inventor is aware are:
U.S. Pat. No. 5,308,365 to Kesling Jr. et al.; PA1 U.S. Pat. No. 5,578,090 to Bradin; PA1 U.S. Pat. No. 5,520,708 to Johnson et al.; PA1 U.S. Pat. No. 5,476,971 to Gupta; PA1 U.S. Pat. No. 5,413,634 to Shawl et al.; PA1 U.S. Pat. No. 5,160,506 to Schur et al.; PA1 U.S. Pat. No. 3,168,385 to Giammaria et al.; and PA1 U.S. Pat. No. 5,145,563 to Culbreth III et al. The 708 Patent to Johnson et al. describes reaction of triglycerides with methanol in the presence of base to produce fatty acid methyl esters, and then describes a specific treatment to reduce "Cloud-Point". However, no mention of the use of ethers of glycerol as an agent to reduce "Cloud-Point" is found therein. The 971 Patent to Gupta describes reacting pure glycerol with isobutylene in the presence of an acid catalyst in a two phase reaction to produce mono-, di- and tri-tertiary butyl ethers of glycerol. The 090 Patent to Bradin describes to reduce fatty acid methyl ester content, and the 365 Patent to Kessling describes the use of Glycerol ethers mixed with Biodiesel fuels to improve emissions content, although no indication of improved Cloud-point or viscosity properties were noted. Said 365 Patent describes reduction of particulate, hydrocarbon, carbon monoxide and unregulated aldehyde content in tests on diesel fuel in which ethers of glycerol were present. The use of ethers of glycerol as extractive distillation agent is described in the 563 Patent to Culbreth III et al., and the 634 Patent to Shaw et al. describes use of ethers of glycerol as an additive to enhance physical properties of cement. The 506 Patent to Schur et al. describes a fuel for use in two stroke engines and comprises oils or ester oils. The 385 Patent to Giammaria et al. describes an anti-knock "appreciator" which combines ethers and alkyl esters. PA1 a. providing a quantity of triglycerides; PA1 b. performing transesterification of at least some of said triglycerides to produce a mixture of biodiesel fuel and crude glycerol; PA1 c. separating out, in an essentially pure state, most of said ester biodiesel fuel from said mixture of biodiesel fuel and crude glycerol leaving a mixture of crude glycerol with some amount of said ester biodiesel fuel; PA1 d. performing etherification of the glycerol in said mixture of crude glycerol with some amount of said ester biodiesel fuel; and PA1 e. remixing the resulting mixture of glycerol ethers with some amount of ester biodiesel fuel produced in step d. With the step c. separated out, essentially pure state, ester biodiesel fuel; PA1 f. after step d, and before step e., separating out unwanted double hydroxyl group containing ethers of glycerol produced in step d., leaving ethers of glycerol with no more than one hydroxyl group present, prior to remixing the resulting mixture of glycerol ethers with some amount of ester biodiesel fuel present with the step c. separated out, essentially pure state, ester biodiesel; and PA1 g. diverting some of the crude glycerol produced in the step b. transesterification of said triglycerides and which is separated out in step c. prior to performing the etherification of remaining crude glycerol in said mixture of crude glycerol in step d.
Alkyl ethers of glycerol have been explored for decades, with references existing back to the 1930's. In addition, it is noted that use of ether derivatives in gasoline reformulation to form oxygenated gasoline, (eg. MTBE & ETBE), is well known. In fact, it is estimated that two-hundred-sixty-thousand (260,000) barrels of methyl (MTBE) Butyl Esters are utilized each day to this end. This is discussed in an article titled "Biodiesel: An Updated Report", by Pearl, Render, June 1996. The rise of (MTBE) production, has produced materials and methods which allow their glycerol based counterpart, (glycerol tertiary butyl ether (GTBE)), to be made easily using an acidic ion exchange resin such as Amberlyst-15. Use of said resin enables high conversion of glycerol and isobutylene into mono-, di-, and tri- tertiary butyl ethers of glycerol. The reaction is more easily taken to high conversions, (no simultaneous distillation as with (MTBE) production), because of the multifunctionality of glycerol and hence stepwise products.
It is noted that known large scale processes for production of Biodiesel fuel largely downplay the significance of the economic loss caused by by-product crude glycerol production, and consider the resulting crude glycerol volume, (which again constitutes approximately twenty (20%) percent of the source triglyceride volume), as something which can be simply discarded, or sold for whatever the market will pay. As costly purification of said crude glycerol is typically necessary to prepare it for third party usage, the price the market will pay is typically minimal. It should then be understood that a process for producing Biodiesel fuel which not only conveniently reclaims said by-product glycerol, but advantageously reclaims it into produced Biodiesel fuel in a way that improves the Biodiesel fuel, would have utility. It is further noted that present invention produced Biodiesel, including glycerol ethers, can be utilized in production of Diesel fuel to produce reformulated Diesel fuel which includes, typically, twenty (20%) percent or more Biodiesel fuel.
No known prior art reference, alone or in combination with other references however, describes, or fairly suggests a process including the use of the product of etherification of crude glycerol produced as a by-product of Biodiesel fuel production, (which Biodiesel fuel is produced by the esterification of renewable triglycerides), as an additive back to said Biodiesel fuel to reduce the Cloud-point, viscosity and pour-point thereof, and to provide cost per volume reducing, maximum Biodiesel fuel volume production, from a given volume of source triglycerides. In addition it is noted that previous methods known to the inventor, for producing methyl esters and glycerol ethers, have been mutually exclusive.
It should be apparent that even in view of known prior art, there remains a need for a procedure which enables the use of crude glycerol, (produced as a by-product of a Biodiesel fuel producing esterification of renewable triglycerides procedure), as a pour-point, viscosity and Cloud-point temperature reducing Biodiesel fuel volume maximizing, cost per volume reducing, additive to said produced Biodiesel fuel. Such a procedure would provide economic and operational benefits, and provide a Biodiesel fuel with properties more closely resembling those of Diesel fuel.